This invention generally relates to storage bags that have means for evacuation. In particular, the invention relates to evacuable storage bags that are reclosable by means a plastic zipper.
Reclosable plastic zippers are useful for sealing thermoplastic pouches or bags. Typically, the plastic zippers include a pair of interlockable fastener elements, or profiles, that form a closure. The profiles in plastic zippers can take on various configurations, e.g. interlocking rib and groove elements having so-called male and female profiles, interlocking alternating hook-shaped closure elements, interlocking ball-shaped closure elements, etc.
For many packaged products, it is desirable to provide means for hermetically sealing the package. For example, it is known to provide a frangible hermetic seal in an unopened reclosable package that contains perishable material, such as foodstuff. However, once the frangible hermetic seal is broken and the package is opened, the hermetic seal cannot be restored when the package is reclosed.
It is also known to store articles of manufacture, such as clothing, in evacuated storage bags having a reclosable zipper. In the case of reclosable storage bags that are evacuated after filling, it is desirable that the reclosed bag be hermetically sealed. Such a hermetic seal must be provided by the plastic zipper. Since it is desirable that such storage bags be reusable, it should be apparent that a one-time frangible hermetic seal is unsuitable.
A known evacuable storage bag relies on zipper profiles that provide mechanical closure and a secondary seal, along with the collapsed packaging film at the bag headspace, which acts as the primary method of sealing the interior volume of the bag from ambient air. The problem with the zipper profiles is that they fail to act as an adequate gas seal when the zipper profiles are distorted, either by the zipper stomping operation or when the bag is folded in half during either final packaging or when used by the customer. Also, on very wide bags, due to unequal elongation when the user improperly closes the zipper with the slider, sometimes the zipper is left partially open. After being distorted, the interconnected and pressed together profiles spread apart and lose their ability to seal off the ambient air. Even the relatively thick (2.5 mils) film at the headspace of the bag, when folded, can create a channel leaker or path for the air to leak into the bag.
There is a continuing need for improvements in resealable zipper designs that provide vacuum-tight sealing of an evacuable storage bag.